Harvey Two-Face Dent is a fictional supervillain appearing in American comic books published by DC Comics, commonly as an adversary of the superhero Batman. The character was created by Bob Kane and Bill Finger, and first appeared in Detective Comics #66 (Aug. 1942).
reactivity. 1  the quality or condition of being reactive. 2  Chemistry. the relative capacity of an atom, molecule, or radical to undergo a chemical reaction with another atom, molecule, or compound. 3  Physics. a measure of the deviation from the condition at which a nuclear reactor is critical.
Full Definition of REACTION. 1. a: the act or process or an instance of reacting b: resistance or opposition to a force, influence, or movement; especially: tendency toward a former and usually outmoded political or social order or policy.2.. : the force that a body subjected to the action of a force from another body exerts in the opposite direction. 4. a (1) : chemical transformation or change: the interaction of chemical entities (2) : the state resulting from such a reaction b: a process involving change in atomic nuclei.